It depends on the workout for me. When I’m in shape of course, if I’m not in shape then it’s hell.
Running 4-6km is very neutral, nothing special
Running 6-10km is kinda enjoyable
Running 10-15km feels really good for some reason
Then everything above 15km is hell (I only ever ran a half marathon at once)
I find running a bit like meditation, or I just let my mind wander wherever. I can’t really put to words the experience, but I would definitely describe it as enjoyable. Especially in winter, I absolutely love it when the cold bites my skin as I start running, and then when you warm up you don’t feel it anymore.